It depends on where the player is in his development cycle. If he developed recently (you’ll see a new “regular season” ratings line in his profile), he likely won’t get a promotion bump, but he also won’t take a hit if you demote him. If it’s been a while since his last ratings bump, a promotion gives him a bump that basically takes the place of that development cycle. The flip side is that he’ll take a ratings hit if you demote him. So check when his last “regular season” ratings line posted before moving anyone.